The search for the molecule or molecules responsible for formation of bone, cartilage, tendon and other tissues present in bone and other tissue extracts has led to the discovery of a novel set of molecules called the Bone Morphogenetic Proteins (BMPs). The structures of several proteins, designated BMP-1 through BMP-13, have previously been elucidated. The unique inductive activities of these proteins, along with their presence in bone, suggests that they are important regulators of bone repair processes, and may be involved in the normal maintenance of bone tissue. There is a need to identify additional proteins which play a role in forming other vital tissues. Recently, the BMP-12-related subfamily of proteins, including BMP-13, was shown to have tendon/ligament-like tissue inducing activity, and to be useful in compositions for the induction of tendon/ligament-like tissue formation and repair. Surprisingly, the present inventors have found that members of this subfamily are also effective for the induction of cartilaginous tissue, and thus are useful for the treatment of diseases or defects of cartilaginous tissue. In particular, the inventors have found that BMP-13 or VL-1 is particularly effective for the induction of cartilaginous tissue. In addition, the inventors have found that BMP-9 is useful for increasing proteoglycan matrix synthesis, and is therefore useful for the maintenance of cartilaginous tissue.